Novel electrostatic dry lift-off and transfer route for vertically aligned nanocomposite oxide thin films.

Highly oriented oxide thin films hold substantial relevance to a wide range of fields. A major challenge is their integration with technological substrates, such as flexible polymers and silicon. While multiple strategies for the lift-off and transfer of high-quality oxide thin films have been widely explored, it remains a challenge to easily transfer films with low defect levels. In this work, we introduce a novel and effective strategy for achieving high-quality, freestanding perovskite oxide thin films. We first demonstrate that highly oriented perovskite oxides, as both single-phase films and vertically aligned nanocomposite (VAN) films, can be grown by pulsed laser deposition on single crystal NaCl, as not shown before. We next show that the VAN films, unlike single-phase films, can be readily, electrostatically, dry lifted-off the substrate. The success of the lift-off technique is enabled by (i) a high thermal expansion mismatch of the film, producing compression in the film, and (ii) lack of elastic strain relief in the out-of-plane direction in the VAN film. Finally, we show that a VAN cathode film can be incorporated into a proof-of-concept micro-solid oxide fuel cell structure, and that it is of good structural quality as demonstrated by performance comparable to equivalent VAN films grown on single crystal YSZ. Thus, we developed an entirely new way to lift-off and transfer highly oriented oxide thin films for use in a wide variety of electronic applications.